MANOMETRY AND ELECTROPHYSIOLOGIC STUDIES
Manometry and electrophysiologic studies are methods for eval-uating patients with GI motility disorders. The manometry test measures changes in intraluminal pressures and the coordinationof muscle activity in the GI tract. The pressures can be recorded manually, on a physiograph, or on a computer.
Esophageal manometry is used to detect motility disorders of the esophagus and the lower esophageal sphincter. Patients must refrain from eating or drinking for 8 to 12 hours before the test. Medications that could have a direct affect on motility (eg, cal-cium channel blockers, anticholinergic agents, sedatives) are with-held for 24 to 48 hours. A pressure-sensitive catheter is inserted through the nose and is connected to a transducer and a video recorder. The patient then swallows small amounts of water while the resultant pressure changes are recorded.
Gastroduodenal, small-intestine, and colonic manometry are used to evaluate delayed gastric emptying and gastric and in-testinal motility disorders such as irritable bowel syndrome or atonic colon. This is often an ambulatory outpatient procedure lasting 24 to 72 hours. Anorectal manometry measures the rest-ing tone of the internal anal sphincter and the contractibility of the external anal sphincter. It is helpful in evaluating patients with chronic constipation or fecal incontinence and is useful in biofeedback for the treatment of fecal incontinence. It can be performed in conjunction with rectal sensory functioning tests. Phospho-Soda or a saline cleansing enema is administered 1 hour before the test. Positioning for the test is either the prone or the lateral position.
A rectal sensory function test is used to evaluate rectal sensory function and neuropathy. A catheter and balloon are passed into the rectum, and the balloon is inflated until the patient feels distention. Then the tone and pressure of the rectum and anal sphincter are measured. The results are especially helpful in the evaluation of patients with chronic constipation, diarrhea, or incontinence.
Electrogastrography, an electrophysiologic study, also may be performed to assess gastric motility disturbances. Electrodes are placed over the abdomen, and gastric electrical activity is re-corded for up to 24 hours. Patients may exhibit rapid, slow, or irregular waveform activity. Electrogastrography can be useful in detecting motor or nerve dysfunction in the stomach.
Defecography measures anorectal function. Very thick barium paste is instilled into the rectum, and then fluoroscopy is per-formed to assess the function of the rectum and anal sphincter while the patient attempts to expel the barium. The test requires no preparation. The use of scintigraphic techniques to measure rectal emptying of radioisotope-labeled artificial stool can provide more quantitative information.
Electromyographic (EMG) studies can supplement anorectal manometry to measure the integrity and function of the anal sphincters in an effort to treat functional bowel incontinence and constipation.